1. Field of the Invention
This invention relates to methods for repairing eroded bottoms of ingot molds. More particularly, this invention relates to a method for forming welded inserts in the bottom of eroded portions of ingot molds.
2. Description of the Prior Art
Various types of molds for preparation of steel ingots are conventionally used in steel mills. For example, various types of big end up molds, such as, open bottom, closed bottom, and plug bottom, are known. In the closed bottom and plug bottom molds, the bottoms thereof are subject to severe deterioration from the impact of the molten steel as it is poured into the mold. Thus, while such solid bottom molds have proved themselves to be essential in the production of certain types of steel, these type of ingot molds are expensive to produce as well as expensive to use in that their overall life expectancy is low.
A major reason for this is that many times, the center of the bottom of the closed bottom and plugged bottom mold is eroded away by the stream of molten steel as the ingot is poured. Such erosion of the bottom is troublesome as well as costly.
Thus, frequently, even though the bottom has not broken out, i.e., the erosion has not gone completely through the bottom of the mold, the indentation due to the erosion will cause the ingot to stick in the mold rendering normal ingot stripping procedures difficult or useless. In such a case, it is sometimes necessary to destroy molds in order to remove the ingot therefrom.
Additionally, as the mold is reused, the eroded portion increases in size and produces a protrusion on the bottom of the ingot which often represents unusable steel after removal of the ingot. The amount of such unusable steel in this protrusion, over the life of the ingot mold, can amount to an entire ingot of steel or more.
Efforts at repairing such molds have generaly been unsuccessful since the bottom of the repaired mold must possess essentially the same strength as the bottom of a new mold. Consequently, relatively expensive welding procedures have been used to repair such molds and, from an economic point of view, have not proved to be successful. Consequently, the life of the molds are substantially shortened since unsatisfactory economics discourage the regular repair of such molds by conventional expensive welding procedures.